The objective of this study is to elucidate the essentiality of essential fatty acids (polyunsaturated acids) through study of the effects of positional and geometric isomerism upon metabolism of unsaturated fatty acids. A secondary objective is elucidation of metabolism function of unsaturated unnatural trans fatty acids currently being consumed in large amounts by people in industrialized countries. The study of the effects of double bond position and geometry upon metabolic fate of unsaturated acids speaks to both these objectives. Therefore, radio-labelled positional isomers of cis and trans unsaturated acids are being synthesized for comparative studies of their metabolism in enzymatic systems in vitro. Enzymes to be used in these comparisons are lipases, acyl transferases and desaturation and chain elongation by liver microsomes. The effects of trans and acetylenic acids upon enzymatic processes will also be studied for their possible inhibitory effects. BIBLIOGRAPHIC REFERENCES: Essential Fatty Acid Deficiency in Animals. R. T. Holman. Handbook of Nutrition and Food, CRC Press, in press, 1977. The deficiency of essential fatty acids. R. T. Holman, in "Polyunsaturated Fatty Acids," Ed., W. Kunan and R. T. Holman. Am. Oil Chem. Soc. Monograph No. 4, 1977, pp. 163-182.